// SPDX-License-Identifier: GPL-2.0
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/*
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* arch/sh/boards/dreamcast/rtc.c
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*
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* Dreamcast AICA RTC routines.
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*
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* Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
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* Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
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*/
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#include <linux/time.h>
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#include <linux/rtc.h>
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#include <linux/io.h>
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#include <linux/platform_device.h>
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/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
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seconds) to get the standard Unix Epoch when getting the time, and add
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20 years when setting the time. */
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#define TWENTY_YEARS ((20 * 365LU + 5) * 86400)
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/* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
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registers.*/
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#define AICA_RTC_SECS_H 0xa0710000
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#define AICA_RTC_SECS_L 0xa0710004
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/**
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* aica_rtc_gettimeofday - Get the time from the AICA RTC
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* @dev: the RTC device (ignored)
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* @tm: pointer to resulting RTC time structure
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*
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* Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
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*/
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static int aica_rtc_gettimeofday(struct device *dev, struct rtc_time *tm)
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{
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unsigned long val1, val2;
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time64_t t;
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do {
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val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
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(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
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val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
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(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
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} while (val1 != val2);
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/* normalize to 1970..2106 time range */
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t = (u32)(val1 - TWENTY_YEARS);
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rtc_time64_to_tm(t, tm);
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return 0;
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}
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/**
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* aica_rtc_settimeofday - Set the AICA RTC to the current time
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* @dev: the RTC device (ignored)
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* @tm: pointer to new RTC time structure
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*
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* Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
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*/
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static int aica_rtc_settimeofday(struct device *dev, struct rtc_time *tm)
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{
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unsigned long val1, val2;
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time64_t secs = rtc_tm_to_time64(tm);
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u32 adj = secs + TWENTY_YEARS;
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do {
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__raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
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__raw_writel((adj & 0xffff), AICA_RTC_SECS_L);
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val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
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(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
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val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
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(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
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} while (val1 != val2);
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return 0;
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}
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static const struct rtc_class_ops rtc_generic_ops = {
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.read_time = aica_rtc_gettimeofday,
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.set_time = aica_rtc_settimeofday,
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};
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static int __init aica_time_init(void)
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{
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struct platform_device *pdev;
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pdev = platform_device_register_data(NULL, "rtc-generic", -1,
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&rtc_generic_ops,
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sizeof(rtc_generic_ops));
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return PTR_ERR_OR_ZERO(pdev);
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}
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arch_initcall(aica_time_init);
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